Self-contained die cushion with air saver



Aug. 18,, 1970 D. T. RYMSZ A 3,

SELF-CONTAINED DIE CUSHION WITH AIR SAVER Filed Nov. 13, 1967 INVENTOR. DANIEL T. RYMSZA ATTORNEYS.

United States Patent O" 3,524,635 SELF-CONTAINED DIE CUSHION WITH AIR SAVER Daniel T. Rymsza, West Chester, Pa., assignor, by mesne assignments, to Gulf & Western Industrial Products Company, Grand Rapids, Mich., a corporation of Delaware Filed Nov. 13, 1967, Ser. No. 682,145 Int. Cl. F16f 9/06 US. Cl. 267-419 9 Claims ABSTRACT OF THE DISCLOSURE I The present invention relates to the art of die cushions and more particularly to a self-contained die cushion having an air saver incorporated therewith.

This invention is particularly applicable for use in a power press wherein depending rods are used to support the hold-down ring of a drawing die and it will be described with particular reference thereto; however, it is to be appreciated that the invention has much broader application and may be used in various other environments wherein a die cushion is required.

Many dies used within power presses incorporate hold down rings or other auxiliary elements which are controlled to a certain extent by a die cushion located below the bed of the power press. The die cushions take a variety of forms; however, the most common die cushion 'includes two telescoped sleeves defining an internal cushion chamber filled with a compressible fluid which biasesthe upper sleeve, or pressure pad, in an upwardly direction. A plurality of rods extending downwardly from the die within the press, rest upon the upper sleeve. These rods coact with movable elements within the die so that the sleeve is forced downwardly by the rods during the downward stroke of the press. The downward movement of the upper sleeve or pressure pad compresses the fiui d within the cushion chamber so that the rods are forced in an upward direction by the upper sleeve during the upward stroke of the power press. The volume of air or other compressible fluid within the chamber of the die cushion is quite large to provide the necessary biasing action for the downwardly extending rod.

When a die is to be repaired or replaced, the die cushion must be dropped to an inoperative position. One common way of accomplishing this is to exhaust most of the fluid in the chamber of the die cushion. This presents a substantial difliculty since a relatively long period of time is required to exhaust and then replace the large volume of fluid within the die cushion. In an effort to reduce the time for exhausting and filling the chamber of the die cushion, relatively large supply hoses have been employed. These are expensive and they do not substantially reduce the total time required to drop the die cushion to its inoperative position and then raise the die cushion back to its operative position.

To overcome the disadvantages of this particular arrangement, it has been suggested that a fluid reservoir should be mounted adjacent the die cushion with a valve between the reservoir and the cushion. When the die cushion is to be dropped, the valve is opened to store the compressible fluid within the reservoir. The valve is then closed so that the fluid remains in the reservoir. To raise the die cushion, the valve is again opened which allows the flow of compressible fluid back to the die cushion. Although this arrangement is satisfactory in some respects, it involves complex and expensive mechanical apparatus to accomplish the operation of the die cushion.

The disadvantages of the prior art die cushions are completely overcome by the present invention which is a wholly new concept to the art of die cushions and includes structure which greatly reduces the required time for dropping the die cushion from its upward operative position to its lower inoperative position and also reduces the time required to raise the cushion back to its operative position. 1

The present invention is particularly advantageous over the prior art approaches in that all of the compressible fluid used for biasing the upper sleeve is retained within the interior of the die cushion even when the cushion is dropped to its lower inoperative position. Thus, the primary object of the present invention is the provision of a self-contained die cushion which is inexpensive to produce, usable in existing presses with very little modification, and easily and rapidly dropped to the inoperative position and raised to the operative position without the need for supplying additional fluid to the cushion.

Another object of the present invention is the provision of a self-contained die cushion in which additional compressible fluid need not be supplied to the die cushion to shift the cushion from the inoperative position to the operative position.

A further object of the present invention is the provision of a self-contained die cushion which employs two separate fluid compartments in the cushion, with a compressible fluid in one of the compartments to provide the 'biasing action on the pressure pad while an incompressible fluid is provided in the other compartment to support the cushion in the operative position.

Still a further object of the invention is the provision of a self-contained die cushion which incorporates two separate fluid compartments in the cushion chamber, both of which cooperate to maintain the cushion in its operative position and only one of which is exhausted to permit the cushion to drop to its inoperative position.

Still another object of the invention is to provide a selfcOntained die cushion which incorporates two separate fl'uid compartments in the cushion chamber with the two compartments being isolated from each other and a compressible fluid in one of the compartments and an in compressible fluid in the other of the compartments.

These objects, as well as others which will become more apparent upon a complete reading of the following description, are achieved in a self-contained die cushion which includes a movable operative member having an inoperative lower position and an operative upper position with a fluid means for moving the member to its operative position and biasing the member in the upper direction when the member is in the operative position. In accordance with this invention, the die cushion includes a cushion chamber divided into first and second chamber portions by a movable piston. An incompressible fluid is disposed on one side of the piston and compressible fluid is disposed on the other side of the piston with the compressible fluid being compressed by the piston and biasing the movable member in the upper direction. Control means are provided to exhaust the incompressible fluid from the die cushion to lower the operative member to its inoperative position while the,

compressible fluid is retained within the die cushion.

A die cushion constructed in accordance with the invention provides a simple means whereby all of the compressible fluid is retained within the die cushion not only when the cushion is in its operative position but also when it is dropped to its inoperative position. Accordingly, the necessity for the time consuming process of exhausting the compressible fluid from the large chamber in the die cushion to drop the cushion to its inoperative position is entirely obviated as also is the process of refilling the chamber with compressible fluid to raise the cushion back to its operative position.

The objects and advantages above stated, as well as others which will be apparent to those having ordinary skill in the art, will best be understood from the follow ing description used to illustrate the preferred embodiment of the invention when read in connection with the attached drawings in which like reference numerals indicate like parts in the various views:

FIG. 1 is a partial cross-sectional side elevation view illustrating, somewhat schematically, the preferred embodiment of the present invention with the die cushion raised to its operative position.

FIG. 2 is a view similar to FIG. 1 illustrating the die cushion in its inoperative position.

Referring now to the drawings wherein the showing is for the purpose of illustrating the preferred embodiment of the invention only and is not for the purpose of limiting the same, there is illustrated a die cushion A constructed in accordance with the present invention. The die cushion A is mounted on a support plate, schematically illustrated at B, which is attached to the frame of a press bed in conventional manner. The general operation of the die cushion is well known in the power press art and, accordingly, a further discussion of the press itself except with regard to the general operation of the die cushion is believed to be unnecessary.

The die cushion comprises a stationary upwardly opening cylinder over which is telescopically received a movable upper sleeve or pressure pad 11. The pressure pad forms the operative member of the die cushion and includes an upper end wall 12, the upper surface of which is adapted to contact the lower end of operating rods in a manner well known in the power press art.

The support plate B provides an end closure plate for the lower stationary cylinder 10. The cylinder 10 includes a central bore 14 and a coaxial counterbored portion 15 with a transversely extending shoulder 16 defined at the juncture of the bore 14 and the counterbore 15. The bore 14, the counterbore 1'5 and the central chamber 18 in the interior of the pressure pad 11 all cooperate to define a die cushion chamber.

The die cushion chamber is divided into two chamber portions by a movable piston 20 which is received in the counterbore 15 in the stationary cylinder 10. The base plate B and the shoulder 16 define lower and upper limits, respectively, for the reciprocation of the piston 20 in the counterbore 15. Appropriate seals 21 are provided on the outer periphery of the piston 20 to seal the juncture between the piston and the side wall of the counterbore 15. The piston 20 thus divides the die cushion chamber into a first chamber portion 24 and a second chamber portion 26.

The piston 20 is generally circular in configuration with an upstanding central portion 28 formed integrally therewith. The central portion 28 includes a recess 30. Disposed in the recess 30 and spaced from the walls thereof is a cylindrical piston portion 32 which defines a secondary piston. This secondary piston is cup-shaped in configuration with an end wall 34 and a central recess 36 defined by the side walls. The secondary piston 32 is secured by appropriate means to the end wall of the recess 30 in the piston 20.

Secured to the base plate is a secondary cylinder 40 having an interior space 42 with the inner diameter of the cylinder 40 corresponding to the outer diameter of the secondary piston 32. The outer diameter of the cylinder 40 corresponds to the inner diameter of the recess 30 with the secondary piston 32 and the secondary cylinder 40 being coaxially aligned so that the piston 32 may be received telescopically within the cylinder 40, as is apparent from inspection of FIG. 1. Appropriate seals 44 carried on the interior wall of the cylinder 40' cooperate with the piston 32 to retain the fluid in the chamber 42. Thus, it will be seen that the piston 20 is mounted for reciprocation relative both to the stationary cylinder 10 as well as the secondary cylinder 40.

A fluid conduit 50 is connected to an appropriate aperture 52 in the base plate B to introduce fluid to the interior 42 of the stationary cylinder 40. The conduit 50 is connected to an appropriate source of fluid with the introduction of fluid to the cylinder 40 being controlled by an air saver valve 54. As illustrated, the source of fluid comprises a control cylinder 56 in which there is received a control piston =58. An appropriate, substantially incompressible, fluid is placed in the cylinder 56 with the control piston 58 being operative to force the fluid through the conduit 50 into the cylinder 40. Movement of the piston 58 is controlled by the introduction of air pressure through the port 60 in the cylinder 56.

The remaining portion of the chamber 26 external to the cylinder 40 is maintained at atmospheric pressure through a vent opening 62 in the wall of the stationary cylinder 10.

The chamber portion 24 is adapted to receive a compressible fluid introduced by appropriate means. The compressible fluid serves to bias the pressure pad 11 in an upward direction at least when the die cushion is inits operative position. Appropriate apertures 64 are formed in the end wall of the piston 20 to provide fluid communication between the interior of the secondary piston 32 and the chamber portion 24.

A rod 66 is threaded at one end to the end wall 12 of the pressure pad 11 with the other end of the rod passing through an aperture 68 in the piston 20 into the interior 36 of the secondary piston 32. A cross 'bar 70 carried by the end of the rod 66 prevents the rod from being withdrawn through the aperture 68 but permits the rod to move inwardly to the interior of the secondary piston 32, as shown in dotted lines in FIG. 1.

Referring now to the operation of the die cushion A during normal operation of the cushion, the chamber 42 in the cylinder 40 is filled with a substantially incompressible fluid by rotating valve 54 and introducing air pressure to the control cylinder 56 whereby the piston 58 forces the fluid into the chamber. The fluid acts on the secondary piston 32 to move the piston 20 to the position shown in FIG. 1. A compressible fluid, preferably air under pressure, is introduced to the chamber portion 24 with this fluid serving to bias the pressure pad 11 to its raised position wherein the die cushion is operative. During normal operation of the die cushion, the pressure pad 11 reciprocates a certain distance relative to the lower cylinder 10 due to the upward and downward movement of the press. The dotted line position of the pressure pad 11 shown in FIG. 1 illustrates the downward movement of the pressure pad during operation of the press. This reciprocating movement compresses the fluid in the chamber 24 with the compressed fluid thereafter forcing the pressure pad in an upward direction as the press starts the upper portion of its cycle. Since the fluid disposed in the cylinder 40 is substantially incompressible, it will be appreciated that the piston 20 remains in its elevated position shown in FIG. 1 during normal operation of the press. Such movement of the rod 66 as may be necessary to accommodate the reciprocating movement of the pressure pad 11 is permitted by the sliding engagement of the rod 66 in the aperture 68. This, then, is the general operation of the die cushion; however, when the die is to be replaced or repaired, it is necessary to drop the die cushion to a lower position.

In accordance with this invention, the die cushion is moved to its inoperative position quickly and easily simply by rotating the air saver valve 54. When valve 54 is rotated, the fluid in the cylinder 40 is free to be displaced through the conduit 50 back to the control cylinder 56. Due to the weight of the pressure pad 11 as well as the pressure of the fluid in the chamber 24, the piston 20 is moved downward to evacuate the cylinder 40. Any air disposed in the remainder of the chamber portion 26 is vented through the aperture 62 to the atmosphere so that the downward movement of the piston is not unduly impeded. As the cylinder 20 is moved downwardly, the upward bias on the pressure pad 11 exerted by the previously compressed air in chamber 24 is relieved so that the pressure pad may also move downward to its inoperative position. The inoperative position of the die cushion with the fluid exhausted from the cylinder 40 is illustrated in FIG. 2.

It will be appreciated that the rate of descent of the pressure pad 11 may be controlled by the degree to which the passage in the valve 54 is aligned with the conduit 50. Moreover, the cushion descent may also be controlled by varying either the size of the passage through the valve 54 or the size of the conduit 50. In this manner it is possible to obtain either a rapid or a carefully controlled descent of the pressure pad. A further control of the rate of descent is available by varying the air pressure on the control piston 58.

To again render the die cushion operative, it is only necessary to rotate the valve 54 to the position shown in FIG. 2 and supply a small amount of air to the control cylinder 56 whereby the piston 58 is moved to the left, as shown in FIG. 2, to force the fluid back into the cylinder 40. As the fluid moves into the cylinder 40, it coacts with the secondary piston 32 to move the piston 20 back to the position shown in FIG. 1. Movement of piston 20 compresses the fluid in the chamber portion 2.4 which, in turn, biases the pressure pad 11 back to its operative position. It is apparent that there is no need to supply any additional compressible fluid to the die cushion to render the cushion again operative.

From the foregoing description, it will be appreciated that the objects set forth have been fully achieved by the described die cushion. Thus, all of the compressible fluid in the die cushion is preserved when the cushion is moved from an operative position to an inoperative position. The only requirement for air pressure once the die cushion has been initially filled is for the very small amount of air pressure required to operate the control piston 58. With this single exception, the die cushion presents a completely closed circuit with the interior chamber of the die cushion serving not only its normal function of biasing the pressure pad but also as a reservoir to save the compressible fluid when the die cushion is inoperative. Moreover, since the only volume of fluid which is displaced during the movement of the cushion from its operative to its inoperative position is the small amount of fluid in the cylinder 40, only a very short period of time is required to shift the die cushion from one position to another.

Although the present invention has been described in connection with one structural embodiment, it is to be understood that various changes may be made in this embodiment without departing from the intended spirit and scope of the invention as defined in the appended claims.

Having thus described my invention, I claim:

1. In a self-contained die cushion including a stationary member and a movable operative member received over said stationary member with said members cooperating to define a cushion chamber therebetween, said operative member having an inoperative lowered position and an operative upper position, the improvement comprising:

piston means dividing said chamber into first and second portions,

said piston means being movable in said chamber,

substantially incompressible fluid in one of said chamber portions for biasing said piston means in one direction and a compressible fluid in the other of said chamber portions for biasing said movable member in an upward direction, and

means for controlling the introduction and evacuation of the incompressible fluid to and from said one chamber portion while retaining the compressible fluid in the other of said chamber portions.

2. The improvement of claim 1 and further including means interconnecting said piston means with said movable; member.

The improvement of claim 2 wherein said interconnecting means includes,

means permitting movement of said movable member relative to said piston means in a direction opposite to said one direction.

-4. The improvement of claim 1 wherein said piston means includes a secondary piston portion,

a cylinder in said one chamber portion telescopically receiving said secondary piston portion.

5. The improvement of claim 4 wherein said source of incompressible fluid is connected only to said cylinder, and

vent means venting the remainder of said one chamber portion to the atmosphere. 6. The improvement of claim 1 wherein said control means includes a control valve and control piston.

7. The improvement of claim 1 wherein said piston means includes a secondary piston portion, said one chamber portion including a cylinder in which said piston portion is received,

said sources of incompressible fluid being connected only to said cylinder, and

means interconnecting said piston means with said movable member,

said interconnecting means including means permitting movement of said movable member relative to said piston means in a direction opposite to said one direction.

'8. The improvement of claim 3 wherein said interconnecting means includes a rod connected at one end to said movable member,

an opening in said piston means,

the other end of said rod extending through said opening in said piston means, and

means preventing withdrawal of said rod through said opening.

9. The improvement of claim 7 wherein said secondary piston portion includes a hollow interior space defined therein,

said interconnecting means including a rod connected at one end to said movable member,

the other end of said rod extending through an opening in said piston means into the interior or said secondary piston portion, and

means preventing withdrawal of said rod from the interior of said piston portion.

References Cited UNITED STATES PATENTS 2,488,047 11/1949 Wissmann.

JAMES B. MARBERT, Primary Examiner 

